Ok, I really like that I get to call them dead metaphors. It just sounds cool.
There are two aspects to a dead metaphor:
1. A dead metaphor can be a metaphor in which the speaker and probably most of the listeners/readers no longer know its meaning.
Example: He dialed her phone number.
This is not a true example, since most of us know what it used to mean to dial a phone. Even though we no longer use dials to call someone, the phrase occassional still pops up. In order for this example to become a dead metaphor, it would take, say, a couple generations down the road when all but a few odd people have forgotten where the phrase comes from.
2. Another type of dead metaphor is a metaphor in which there never was a link from the tenure to the vehicle to begin with. I am reminded of a few lines from the movie Chicken Run.
"Like a fish" doesn't have any obvious connection to being all quiet like. It's a dead metaphor.
1. Find a dead metaphor used in every day life.
2. Come up with a metaphor replacement for the rodents' dead metaphor.
We were quiet as......
..........like a fish.
(Hey, that's another choice. Cool.)
Example: We were quiet as the calm before a storm.
We slipped in and out of there like a fish.